By the treatment of water is meant, besides filtration, also the graduated delivery of substances to the water. The delivery of substances can also be combined with a filtration of the water.
By filter cartridges are meant, on the one hand, those which have a sievelike structure for the mechanical filtration. On the other hand, by filter cartridges are meant those which contain, besides a sievelike structure, at least one filter medium, for example one in granulate form, which serves for the chemical and/or mechanical removal and/or reduction of organic and/or inorganic impurities. Thus, filter cartridges of this kind enable a nonmechanical filtration, which can be combined with a mechanical filtration. These filter cartridges are used for optimization of water, meaning by optimization the mechanical and/or nonmechanical filtration. This includes, e.g., the softening and decalcifying of drinking water.
Filtration can be pressure-operated, i.e., it can be carried out with excess pressure, or with partial vacuum, or by gravity forces.
A filter apparatus is known from WO 2007/012079 A2 that has a filter cartridge and a connecting device. The connecting device is generally firmly mounted. The filter cartridge is inserted into this connecting device and after the filter material is used up it is exchanged for a new filter cartridge. The insertion process places a load on the gaskets at the connecting head of the filter cartridge and/or the holder of the connecting device, especially when the inserting process involves a rotational movement of the filter cartridge.
In order to avoid rotational movements, a locking device is proposed that engages with the holder of the cartridge, in which only a translatory movement of the filter cartridge is required both for the installation and the removal of the filter cartridge. This occasions a costly locking device, one working by the principle of a ball point pen, in which the spring device must be configured and arranged so that at least one of the components of the locking device executes a rotational movement.
The water inlet opening of the filter cartridge is disposed at the end face of the connecting head, so that the filter cartridge must be inserted against the direction of flow of the unfiltered water and, thus, against water pressure. In operation of the filter cartridge, the water pressure acts constantly on the filter cartridge and presses it out from the holder. In order to prevent this, yet still fix the filter cartridge securely and immovably in the holder, a stable configuration of the locking device is indispensable. In order to avoid dripping losses when dismounting the filter cartridge, a costly valve construction and a plurality of sealing elements are required.